IPv4 depletion began oficially in the European region as of September 14th 2012, when RIPE NCC* started to allocate IPs from the last /8
* RIPE NCC = Reseaux IP Europeens Network Coordination Centre - the organisation that administrates IP resources for the European region
The solution would have been massive IPv6 deployment which unfortunately didn't happen. Therefore we need to be able to live with IPv4 for several more years.
This need led to the apparition of a new market. The IPv4 transfers market.